1. Field of the Invention
The present invention relates to a data transfer system and a method and, more particularly, to the data transfer system and the method whereby data sent as an isochronous packet over a high-performance serial bus (hereinafter called 1394 bus) standardized in IEEE Std 1394-1995 is transferred via an Asynchronous Transfer Mode (ATM) network to another 1394 bus.
2. Description of the Related Art
By use of isochronous transfer through a high performance serial bus standardized in IEEE Std 1394-1995, it is possible to transmit and receive real-time data such as time-varying images.
Japanese Laid-Open Patent Application No. Hei10-190742 (hereinafter referred to as Literature 1), on the other hand, discloses a data transmission method and an apparatus using the same whereby data can be transmitted using a 1394 bus with an ATM cell sent thereon. By using the data transmission method and apparatus, data can be transferred between terminals connected via an ATM network to the 1394 bus.
Also, Japanese Laid-Open Patent Application No. Hei9-275402 (hereinafter referred to as Literature 2) discloses other apparatuses and methods whereby ATM-standard data is converted into IEEE1394-standard data.
The IEEE Std 1394-1995 standards, however, have such limitations in terms of a number of terminals and a distance as a maximum number of terminals (hereinafter also referred to as nodes) that can be connected to one 1394 bus being 63, a maximum distance between mutually adjacent nodes being 4.5 meters, and a maximum bus length being 72 meters. That is, there occurs such a problem that real-time data cannot be transmitted or received by use of isochronous transfer between terminals with an IEEE1394 interface if they are in excess of the above-mentioned number limit or distance limit.
Standards of Literature 1, on the other hand, have such a problem that there are required such processing of taking out an ATM cell from an isochronous packet and processing of sending an ATM cell onto the isochronous packet, which are not required to communicate data over a 1394 bus to all terminals which each have an interface connectable to that bus. That is, Literature 1 standards suffer a problem that its invention cannot be implemented unless a conventional terminal is provided with a method and an apparatus required to execute above-mentioned two types of processing. Literature 2 refers to no means for solving the above-mentioned problems either.